This invention relates to a printer and a facsimile apparatus using the printer and, more particularly to a printer which prints an image on a print medium in accordance with and ink-jet printing method and a facsimile apparatus using the printer.
An ink-jet printer which performs printing by discharging ink droplets from a printhead, comprising a plurality of nozzles, on a print medium such as a print sheet or an OHP sheet, in accordance with an ink-jet printing method, has advantages such as low running cost, suitability for color printing, and quiet print operation. Therefore, the ink-jet printer is widely used as a printing unit of facsimile apparatuses, copying machines and the like, as well as an output device of computers.
Further, as a printhead of this printer, a monochrome printhead which performs monochrome printing by using only one color ink, e.g., black ink, and a color printhead which supplies yellow, magenta, cyan and black color ink and performs color printing by discharging ink from nozzles assigned to the respective colors have been provided.
Upon applying the printer to a facsimile apparatus, for printing based on received facsimile image information, a mechanism to detect print-disable status such as ink exhaustion and ink-discharge failure is provided. That is, in the conventional technique, to avoid omission of image printing due to ink exhaustion during image printing using received facsimile image data, existence/absence of ink is judged after printing of one page. If it is judged that ink remains, data corresponding to printed image is deleted from an image memory. For this judgment, the printer has a photosensor (photo-interrupter) including a light-emission device comprising an LED or the like and a photoreception device comprising a photo-transistor or the like. As ink-discharge status detection, ink-discharge failure status due to ink exhaustion or status where nozzles are clogged with some foreign materials due to some reasons and printing is not normally performed, is detected by discharging ink so as to interrupt light from the light-emission device, and monitoring change of the light received by the photoreception device.
FIG. 15 is a cross-sectional view showing the structure of a printer included in a facsimile apparatus.
As shown in FIG. 15, a plurality of print sheets P are piled on a cassette 151, and taken out by a paper-feed roller 152, one by one, to a conveyance roller 153, and further, to a printer B. The printer B has a printhead 160 which performs printing in accordance with an ink-jet printing method and which is scanned in a direction (main-scanning direction) orthogonal to a print-sheet conveyance direction. The printhead 160 comprises a large number of nozzles (e.g. 128) in a direction orthogonal to the main-scanning direction (X direction in FIG. 15 is the subscanning direction). Image printing is made by discharging ink from the printhead 160 on the surface of the print sheet P while scanning the printhead 160 in the main-scanning direction. After the completion of image printing, the print sheet P is conveyed by a pair of discharge rollers 154 along a guide 155 in the X direction, and discharged by a discharge roller 156, a discharge rod 157, onto a discharge stacker 158, and stacked there.
The printhead 160 mounted to this apparatus is a cartridge type printhead which includes an ink tank. When ink is exhausted, the printhead can be exchanged for a new printhead with an ink tank. To attain color printing with downsizing of the apparatus main body, the printhead 160 has 64 nozzles to discharge black ink, and respectively 24 nozzles to discharge ink of primary three colors, yellow, cyan and magenta. The respective color ink can be replenished by independently changing small separate ink tanks of respective colors.
Upon applying the printer having this construction to a facsimile apparatus, to ensure print-output of received image information, it is necessary to detect print-disable status such as ink exhaustion and ink-discharge failure. As method for detection, a technique to directly discharge ink between a light-emission device and a photoreception device constituting a photo-interruptive type photosensor has been proposed. The change of output from the photosensor caused by interruption of light from the light-emission device by the discharged ink is detected and ink-discharge abnormality can be judged based on the result of detection.
In the photo-interruptive type photosensor, a lens is integrally molded on a light-emitting surface, so that the light-emission device can irradiate light in approximately parallel toward a photoreception device such as a photo-transistor. On the other hand, the photoreception device has a 0.7xc3x970.7 mm hole formed of a mold member, on the optical axis, on its photoreception surface. That is, a detection area is narrowed to 0.7 mm in height and 0.7 mm in width between the photoreception device and the light-mission device. The optical axis connecting the light-emission device and the photoreception device is set to parallel to the nozzle array of the printhead. The interval between the light-emission device and the photoreception device is wider than the nozzle array of the printhead. When the optical axis and the position of the nozzle array coincide, all ink droplets discharged from the nozzles of the printhead pass the detection area between the light-emission device and the photoreception devices the ink droplets pass the detection area, the ink droplets interrupt light from the light-emission side, and decrease light intensity to the photoreception side, thus the output from the photo-transistor as the photoreception device changes. Since the number of nozzles to discharge ink is approximately proportional to the amount of change of the output from the photosensor, if the variation of the output from the photosensor is equal to a predetermined threshold value or greater, it is judged that in; remains, i.e., xe2x80x9cprint operation has been normally performedxe2x80x9d. In contrast, if the variation of the output from the photosensor is less than the threshold value, it is judged that ink-discharge is poor, i.e., xe2x80x9cprint operation has not been normally performedxe2x80x9d. In this case, further print operation is suspended until recovery operation such as ink-tank change is made, and facsimile reception is stopped or received data is stored into an image memory.
The ink-discharge status detection using the photo-interruptive type photosensor as described above is made such that after the completion of printing for one page of print sheet, ink is simultaneously discharged from all the nozzles necessary for facsimile reception printing, e.g., 64 black-ink nozzles.
Further, in case of judgment of existence/absence of ink with respect to color ink based on the amount of change of output from the photosensor, the judgment is made by using a threshold value common to the respective colors. For the judgment, to improve detection precision, the amount of ink to be discharged is changed in accordance with ink color.
However, when the color printhead is attached to a conventional facsimile apparatus for monochrome image printing, to print an image based on received image data on a print medium, black ink is discharged from only the nozzles assigned to black ink. Accordingly, in comparison with a printhead for monochrome printing (monochrome printhead), the number of black-ink nozzles is smaller. Even if all the nozzles assigned to black ink are used for discharging black ink, ink-discharge amount differs in the two type of printheads, and the degree of interruption of light from the light-emission device differs in the printheads. As a result, an output signal from a photo-transistor used for judgment of existence/absence of ink varies in accordance with the type of printhead attached to the apparatus.
Accordingly, the comparison of the output signal from the photo-transistor with one threshold value cannot attain exact judgment of existence/absence of ink.
Regarding the printer according to an ink-jet printing method, to further utilize the advantage of the printing method, it has a print mode (normal print mode) for discharging ink from all the nozzles of a printhead to form an image and another print mode (economy print mode) for discharging ink from alternate nozzles to form an image with only the half amount of ink used in normal print mode.
On the other hand, residual-ink detection and ink-discharge status detection in the conventional printer is made by discharging black ink necessary for printing based on received facsimile data from all the nozzles assigned to black ink. Even when facsimile-reception printing is performed in the economy print mode, judgment of ink-discharge status on nozzles which are not related to image formation is included in judgment of normal/abnormal printing status.
However, assuming that an average value of the amount of change of the output, obtained from the photoreception device, in case of normal ink discharge from 60% of the all nozzles, is employed as a threshold value for judgment of normal/abnormal print operation, if facsimile-reception printing is performed in the economy print mode, and 30% of all the nozzles are in poor ink-discharge status, further, if most of those poor nozzles are used in actual printing, a control circuit of the facsimile apparatus judges that printing has been normally performed and deletes image data stored in an image memory.
If print operation is performed in the normal print mode, a printed image includes faint portions at about 30%, which causes no problem for practical purpose of legibility; however, in the economy print mode, a printed image includes faint portions at about 60%, which disturbs interpretation of information provided by the printed image. In the latter case, as data is deleted from in the image memory, the information is entirely lost.
Further, in a case where the ink-jet printer is used as a terminal of a computer, if precision of ink-discharge status detection is low, there is a possibility that, in printing a document file of tens of pages in the economy print mode, a large number of images where information is not intelligible at all is outputted. In this case, print-output must be retried, which increases a user""s labor, further, wastes resources such as print sheets and ink, as a result, raises the running cost.
In consideration of the tendency of development of current technologies, it is predicted that color facsimile apparatuses and color printers will greatly become popular in the future. Print control based on residual-ink detection must be directed to, as well as black ink, ink of three primary colors, yellow, cyan and magenta. However, detection precision of residual-ink detection for respective color ink differs in colors unless the following factors are fully considered: (1) a printhead may have a construction where the number of black-ink nozzles and those of nozzles assigned to other color ink are different; (2) light-transmittances of respective color ink are different; (3) variation of output from a photoreception device differs in respective color ink since diameter of nozzle and that of ink droplet are different in respective color so as to form appropriate color image by adjusting tints of respective colors.
For example, as in the conventional printer, if existence/absence of ink is judged by using a threshold value common to the respective color ink, as respective light-transmittances of the respective color ink with respect to the photo-interruptive type photosensor are not considered, the detection result has low reliability. Further, if ink-discharge amount is changed in accordance with ink color, the amount of ink used for ink-discharge status detection differs for each ink color. This causes a problem that particular color ink is consumed in ink-discharge status detection and exhausted earlier than other ink.
Accordingly, the present invention has its object to provide a printer which performs accurate residual-ink detection even if the type of printhead attached thereto is changed.
According to the present invention, the foregoing object is attained by providing a printer which uses one of plural types of exchangeable printheads, and which performs printing by discharging ink from the printhead on a print medium, comprising: an ink tank for containing ink; first discrimination means for discriminating a type of a printhead which is attached to the printer; selection means for selecting one of a plurality of threshold values set in consideration of printing characteristics corresponding to the plural types of printheads, in accordance with the result of discrimination by the first discrimination means; test-discharge means for discharging ink from the printhead as test discharge; detection means for detecting ink droplets discharged by the test discharge means; and second discrimination means for comparing the result of detection by the detection means with the threshold value selected by the selection means, and discriminating ink-discharge status, based on the result of comparison.
In accordance with this aspect of the present invention as described above, when one of plural types of exchangeable printheads is attached to a printer for performing printing by discharging ink on a print medium, the type of the attached printhead is discriminated, and one of plural threshold values, each obtained by considering the printing characteristic of corresponding printhead, is selected, in accordance with the result of discrimination. Then, ink is test-discharged from the printhead, and discharged ink droplets are detected. The result of detection is compared with the selected threshold value, and existence/absence of ink is judged in accordance with the result of comparison.
It may be arranged such that a message advising to change ink tank(s) is displayed in accordance with the result of judgment.
The detection of ink droplets upon test ink discharge is made by using light-emission means for emitting light to a position where the ink droplets discharged from ink-discharge orifices of the printhead pass, photoreception means for receiving the light from the light-emission means, and measurement means for measuring a period in which the light is interrupted between the light-emission means and the photoreception means.
The light-emission means includes an infrared LED, on the other hand, the photoreception means includes a photo-transistor for generating an electric signal based on received light.
Note that the printhead may be an ink-jet printhead which performs printing by discharging ink or a printhead which utilized thermal energy to discharge ink and has electrothermal transducers for generating thermal energy to be supplied to ink.
It is another object of the present invention to provide a facsimile apparatus using the printer having the above construction.
According to another aspect of the present invention, the foregoing object is attained by providing a facsimile apparatus using the above printer, comprising: reception means for receiving image information transmitted via a communication line; memory means for storing image information received by the reception means; and control means for controlling the test-discharge means to perform test ink discharge after completion of each image printing, based on the image information received by the reception means, for one page of print medium.
In accordance with this aspect of the present invention as described above, in reception of facsimile image information by the facsimile apparatus using the printer having the above construction, each time image printing based on the received image information for one page of print medium has been completed, test ink discharge is made to perform ink-discharge status detection.
Then, in accordance with the result of ink-discharge status detection, the received image information stored in the memory means is held or deleted.
It is still another object of the present invention to provide a color printer which releases a user from tiresome operations and ensures printing with high reliability, and low running cost.
According to still another aspect of the present invention, the foregoing object is attained by providing a color printer using a color printhead which performs color printing on a print medium using a plurality of color ink, comprising: instruction means for selecting a first mode to perform printing by using all of a plurality of print elements of the color printhead or a second mode to perform printing by using a part of the plurality of print elements, and instructing the selected mode as a print mode; input means for inputting image data; print means for performing printing on the print medium, based on the image data inputted by the input means, by using the color printhead, in accordance with the print mode instructed by the instruction means; and detection means for, after completion of printing on the print medium, test-discharging all the plurality of color ink from the color printhead, and in consideration of the print mode instructed by the instruction means and ink characteristics of the respective plurality of color ink, based on results of discharge of the plurality of color ink, and detecting whether or not the color printhead is in normally-dischargeable status.
In accordance with this aspect of the present invention as described above, upon printing, the color printhead which performs printing by discharging a plurality of color ink on a print medium is used, and the first mode for printing by using all the print elements of the printhead or the second mode for printing by using a part of the print elements is selected and instructed as a print mode. In accordance with the selected mode, image printing based on input image data on a print medium is performed by using the color printhead. After the printing has been completed, all the plurality of color ink are test-discharged from the color printhead, and based on the result of test discharge, ink-discharge status detection of respective color ink is performed, in consideration of the instructed mode and characteristics of the respective color ink.
Then, in accordance with the result of detection, print operation is controlled, or if it judged that ink is exhausted, a message notifying of ink exhaustion is displayed on, e.g., a LCD.
The ink-discharge status detection is made by using test discharge means for test-discharging all the plurality of color ink from the color printhead, detection means for detecting test-discharged ink droplets, and first discrimination means for discriminating whether or not respective color ink still remain, based on the result of detection by the detection means. Further, upon test ink discharge, the detection of ink droplets is made by using light-mission means which emits light to a position where the ink droplets discharged from ink-discharge orifices of the printhead pass, photoreception means for receiving the light, and measurement means for measuring a time period in which the light is interrupted between the light-emission means and the photoreception means.
The variation of the amount of received light at the photoreception means is measured as analog data, and the measurement means may include an A/D converter for converting the analog data into digital data.
The light-emission means includes an infrared LED, on the other hand, the photoreception means includes a photo-transistor for generating an electric signal based on received light.
Note that the printhead may be an ink-jet printhead which performs printing by discharging ink or a printhead which utilized thermal energy to discharge ink and has electrothermal transducers for generating thermal energy to be supplied to ink.
Further, the plurality of color ink includes black ink, yellow ink, magenta ink, and cyan ink.
Further, the plurality of printing elements of the color printhead include a first nozzle group for discharging black ink, a second nozzle group for discharging yellow ink, a third nozzle group for discharging magenta ink, and a fourth nozzle group for discharging cyan ink. When printing is performed in the first mode, all the nozzles of the first to fourths nozzle groups are used, while in the second mode, the half of the nozzles of the respective first to fourth nozzle groups are used.
It may also be arranged such that in the ink-discharge status detection as described above, the results of ink discharge of the respective color ink are compared by, e.g., using eight threshold values stored in the memory means respectively according to moded and color ink, and existence/absence of respective color ink is judged from the result of comparison.
Note that the means for comparing the discharge results comprises a comparator having a first terminal for inputting a signal indicating the detection results and a second terminal for inputting threshold values for comparison. The threshold values are at least different in accordance with ink color.
Further, the above-described ink-discharge status detection may be performed by using test print means for printing a predetermined pattern at a predetermined position of a print medium, irradiation means for irradiating light to the predetermined pattern, a second photoreception means for receiving reflection light of the light irradiated by the irradiation means, and second discrimination means for discriminating whether ink remains or not, in accordance with the amount of received light amount.
It is still another object of the present invention to provide a facsimile apparatus using the color printer having the above construction.
According to still another aspect of the present invention, the foregoing object is attained by providing a facsimile apparatus using the above color printer, comprising: communication means for transmitting and receiving facsimile image data via a communication line; memory means for storing facsimile image data received by the communication means; and memory control means for controlling deletion of the facsimile image data stored in the memory means.
In accordance with this aspect of the present invention as described above, in the facsimile apparatus using the color printer having the above construction, facsimile image data received via the communication line is stored into the memory means, and the received facsimile image data stored in the memory means is deleted otherwise held in accordance with the result of detection by the detection means.
The invention is particularly advantageous since accurate judgment of existence/absence of ink is possible even though the type of attached printhead is changed.
Further, according to another aspect of the present invention as described above, upon facsimile reception of image information, as ink-discharge status detection is performed by test ink discharge after the completion of each image printing based on the received image information for one page of print medium, whether an image has been normally printed or not can be confirmed for each page. This enables to confirm printing result for each page.
Further, according to still another aspect of the present invention as described above, more accurate ink-discharge status detection is possible in correspondence with print mode and respective ink characteristics.
This prevents printing of an image in degraded image quality due to exhaustion of ink, thus reduces running cost by eliminating unnecessary output. Also this prevents re-output, thus releases a user of the apparatus from tiresome operations.
Furthermore, upon printing facsimile reception image, printing of an image in degraded image quality and undesirable deletion of received image data from an image memory can be prevented. This contributes to facsimile communication with high reliability.